As industry has refined and improved production techniques and procedures, requirements have arisen for placing identifying or data related markings upon components of manufactured assemblies. With such marking, the history of the product may be traced throughout the stages of its assembly.
A variety of product marking approaches have been employed in the industry. For example, paper tags carrying bar codes or the like may be adhesively applied to the components in the course of assembly. However, for many applications, these tags will exhibit poor permanence and abrasion resistance characteristics. Ink or paint spraying of codes such as dot matrix codes are unacceptable for employment in rigorous production environments, inasmuch as they will be expunged in the course of many production procedures. Of course, subsequent printing stages in a production process would nullify the above marking approaches.
The provision of a traceable marking upon hard surfaces such as metal traditionally has been provided with marking punches utilizing dies which carry a collection of full form characters. These "full face dies" may be positioned in a wheel or ball form of die carrier which is manipulated to define a necessarily short message as it is dynamically struck into the material to be marked. As is apparent, the necessarily complex materials involved are prone to failure and full faced dies exhibit rapid wear characteristics. Generally, the legibility and abrasion resistance of the resultant marks can be considered to be only fair in quality. Additionally, the marking punch approach is considered a poor performer in marking such surfaces as epoxy coatings and the like.
Laser activated marking systems have been employed, however, the required equipment is of a relatively higher cost and the abrasion resistance and "readability after painting" characteristics of laser formed characters are considered somewhat poor.
Over the recent past, a computer drive dot matrix marking technique has been successfully introduced into the marketplace. Described in U.S. Pat. No. 4,506,999 by Robertson entitled "Program Controlled Pin Matrix Embossing Apparatus", the marking approach employs a series of seven tool steel punches which are uniquely driven using a pneumatic floating impact concept to generate ASCII characters or reverse font characters which are man readable, as well as linear dot codes which are machine readable. Marketed under the trade designation "PINSTAMP" these devices carry the noted tool steel punches or "pins" in a head assembly which is moved relative to the piece being marked at a selected skew angle to indent a dot or pixel defined permanent message or code into a surface of the marked component. The approach enjoys the advantage of providing characters of good legibility as well as permanence. Further, a capability for forming the messages or codes during forward or reverse head movements is realized. The device provides dot matrix characters of good abrasion resistance, good permanence and legibility and is, advantageously, capable of marking upon such surfaces as epoxy coatings. However, inasmuch as the pin retaining head of this apparatus is required to traverse over a distance representing that between the outside punches or pins plus one character width, the application of the device in a production environment wherein items of multi-faceted shape and small size are encountered is somewhat constrained. Preferably, the apparatus is employed where adequate tracking space is available on the product to be marked. Additionally, because there is a relative movement between the marker head and the item being marked, it is necessary to fixture these two parts to assure proper relative movement therebetween. For some production procedures, for example those employing items hanging from chains and the like, this fixturing involves complexity. To meet the continuously broadening marking requirements of industry, an application of the dot matrix stamping approach which can perform in cramped locations at adequate speeds and with minimal fixturing is desirable.